1. Field of the Invention
The present invention relates generally to a wafer polishing apparatus, and more particularly to a wafer polishing apparatus which is used with a chemical mechanical polishing (CMP) method.
2. Description of Related Art
A wafer polishing apparatus disclosed in Japanese Patent Provisional Publication No. 8-339979 is provided with a holding head (a carrier), a polishing pad (a polishing cloth), and a seal member. Liquid supply passages are formed in the holding head, and a pressurized liquid is supplied into a space enclosed by the holding head, a substrate (a wafer) and the seal member, and the pressurized liquid presses the substrate against the polishing pad.
An annular guide member is attached to the holding head of the wafer polishing apparatus. The guide member as well as the substrate are pressed against the polishing pad so as to prevent the substrate from springing out of the holding head due to a centrifugal force.
The wafer polishing apparatus of Japanese Patent Provisional publication No. 8-339979, however, presses the substrate against the polishing pad only with the pressurized liquid. For this reason, the polishing pressure applied from the polishing pad to the substrate centers on the peripheral edge of the substrate, in other words, the polishing pad rises at the peripheral edge of the substrate. Consequently, the peripheral edge is polished more than an the other parts.